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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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HTML 

              
                <h2>Beastie Boys Anthology</h2>
<p>The Sounds of Science is the first anthology album by American rap rock group Beastie Boys composed of greatest hits, B-sides, and previously unreleased tracks.</p>
<div x-data="{ open: false }" x-cloak>
  <button @click="open = ! open" :aria-expanded="open" aria-controls="tracklist">Tracklist</button>
  <ol x-show="open" id="tracklist">
    <li>Beastie Boys</li>
    <li>Slow And Low</li>
    <li>Shake Your Rump</li>
    <li>Gratitude</li>
    <li>Skills To Pay The Bills</li>
    <li>Root Down</li>
    <li>Believe Me</li>
    <li>Sure Shot</li>
    <li>Body Movin' (Fatboy Slim Remix)</li>
    <li>Boomin' Granny</li>
    <li>Fight For Your Right</li>
    <li>Country Mike's Theme</li>
    <li>Pass The Mic</li>
    <li>Something's Got To Give</li>
    <li>Bodhisattva Vow</li>
    <li>Sabrosa</li>
    <li>Song For The Man</li>
    <li>Soba Violence</li>
    <li>Alive</li>
    <li>Jimmy James (Original Version)</li>
    <li>Three MC's And One DJ (Live Video Version)</li>
  </ol>
</div>
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CSS 

              
                .js [x-cloak] { display: none; }
.no-js button { display: none; }

body {
  overflow-y: scroll;
}
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JS
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999px

Console